1. Field of the Invention
The present invention relates to an image source unit and an image display unit comprising the image source unit.
2. Description of the Related Art
An image display unit which projects an image to the observer side is provided with an image source unit comprising: an image light source; and an optical sheet comprising a layer having various functions for raising the quality of image light emitted from the image light source and projecting the image to the observer side.
For example, in a case of a plasma display as one of the image display units, when the observer side is bright, the contrast of the display is insufficient and thereby the quality of the image is deteriorated. In such a plasma display, an optical functional layer is sometimes provided to the optical sheet of the image source unit so as to improve the contrast. The optical functional layer has light-transmissive portions and light-absorbing portions and can adequately shield the external light. The term “contrast” means the ratio between the brightness of the white portion showing maximum brightness (it is called “white brightness”) and the brightness of the black portion showing minimum brightness (it is called “black brightness”) when displaying black-and-white image.
Such an optical functional layer is disclosed in, for example, Patent document 1 (Japanese Patent Application Laid-open (JP-A) No. 2006-189867) as an external light shielding layer which comprises: a filter base; and an external light shielding layer being formed on one surface of the filter base, and comprising: a transparent resin-made base, and wedge-shaped black stripes arranged parallel on one surface of the transparent resin-made base.
Patent document 2 (JP-A No. 02-097904) discloses a light-control film which is a transparent film and comprises a first and a second main surfaces, wherein the first main surface has a plurality of grooves and the grooves are filled with a light-absorbing material.
Patent document 3 (JP-A No. 2009-058658) discloses an optical sheet comprising a light-transmissive layer having prism lines arranged parallel, wherein each of the width of the prism lines is narrower toward a top end and the intersectant portion of the upper face and the oblique face of the prism lines has roundness having a radius of curvature of 3-30 μm.
Patent document 4 (JP-A No. 2009-080198) discloses an optical sheet which is arranged at an observer side from an image light source and which comprises a plurality of layers controlling the light emitted from the image light source and transmitting the light to the observer side. In the optical sheet, at least one layer of the plurality of the layers is an optical functional layer comprising light-transmissive prism portions arranged parallel along the sheet face and light-absorbing portions arranged between the light-transmissive prism portions; and at least one base of the light-absorbing portion in cross section in the sheet-thickness direction has a recess having a curved or polygonal line so that the at least one side of the light-absorbing portion in cross section in the sheet-thickness direction projects towards the sheet thickness direction.
Patent document 5 (JP-A No. 2008-046644) discloses a plasma display device comprising: a plasma display panel; and a filter formed on the entire surface of the panel, wherein the filter comprises a base unit; and an external light shielding sheet including a plurality of pattern units formed on the base unit, wherein the bottom stage of the pattern unit which is wider than the upper stage of the pattern unit is formed in a recessed shape.